Lithostratigraphy and volcanic evolution of Deception Island, South Shetland Islands

Abstract

Deception Island is the most active volcano in the Antarctic Peninsula region. It is a large basalt–andesite shield volcano with a 10 km-wide restless caldera (Port Foster) and a complicated history of pre- and post-caldera eruptions. There has been no modern volcanological investigation of the entire island and it remains a largely unknown volcanic hazard. The pre-caldera period on the island began with the low-energy eruption of tephras from multiple centres (Fumarole Bay Formation), possibly by subaqueous fire fountaining during shoaling and likely initial emergence of the volcano. It was followed by subaerial effusive to weakly pyroclastic (Strombolian/Hawaiian) activity that constructed a small basaltic shield (Basaltic Shield Formation), and a large eruption that vented about 30 km3 of magma (Outer Coast Tuff Formation). The latter eruption may have been triggered by an influx of compositionally different magma into the main chamber feeding the volcano, and the evidence suggests that it was associated with a significant involvement with water (seawater?). The eruption was followed by caldera collapse, and there have been several small incremental caldera “collapses” subsequently. Post-caldera eruptions were all small-volume and predominantly phreatomagmatic (Baily Head and Pendulum Cove formations), but magmatic eruptions constructed several small lava deltas around the coast and also produced a local carapace of scoria and thin lavas, particularly around the caldera rim (Stonethrow Ridge Formation). Although the caldera is presently resurging, interpretation of the eruptive history of the island suggests that future eruptions are likely to be small in volume and will have only a limited regional impact.

Costa Recta beach, Deception Island, West Antarctica: a retreated scarp of a submarine fault?

“…1c). Both groups were defined in relation to a single episode of caldera collapse (Smellie 2001: 1) Precaldera deposits (Port Foster Group): formed mainly by pillow lava deposits (currently below sea level), products of explosive hydrovolcanic eruptions and pyroclastic flow deposits from large-volume caldera-forming eruption (Smellie 2001.…”

Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes

“…This implies that either no crustal contamination took place during shallow level magma chamber differentiation, or that it occurred at insignificant levels. However, this conclusion is only valid for the geological units from which Keller et al (1992) took their samples, information that could not be given in the respective paper because it was published before the stratigraphy related information (Baraldo and Rinaldi, 2000;Smellie, 2001) became available.…”

“…1.500 m above the sea floor of its highest summit (Mount Pond, 540 m). The initial emergence of the volcano above sea level likely began with low energetic tephra eruptions from multiple centers (Smellie, 2001). Subsequently, a small basaltic shield was formed by subaerial effusive to weakly pyroclastic activity.…”

“…The formation of the 10 km wide caldera (Port Foster) marks a turning point in the complicated history of pre-and post-caldera eruptions, but the timing of this important event is unknown. Whether the caldera formed during a continuous extension process (Rey et al, 1995;Martí et al, 1996) or a single catastrophic event (Smellie, 2001) is still under debate. Terminating the pre-caldera phase, Smellie (2001) argues in favor of a catastrophic caldera forming event producing a minimum of ~30 km 3 , possibly as much as 60 km 3 ) of magma involving substantial amounts of water, likely seawater.…”

Study of the active layer at the Spanish Antarctic station “Gabriel de Castilla”, Deception Island, Antarctica

“…Su origen está relacionado con un sistema de fracturas en el fondo oceánico, a más de 850 m bajo la superficie, de dirección SW-NE en el llamado Arco de Scotia (Hawkes, 1962;Baker et al, 1975;Grad et al, 1992;Rey y Somoza, 1992;Rey et al, 1995;González-Casado et al, 2000;Somoza et al, 2004;Maestro et al, 2007). Todos los materiales presentes en la isla tienen un origen volcánico, hidrotermal o volcanoclástico por la modificación de los dos primeros (Smellie, 2001.…”